It is known that the subsoil, and in particular aquifers, are characterized by the presence of compounds having natural or anthropic origin, whose persistence for prolonged times can generate health problems. Within multiple anthropic activities, such as for example industrial activities, or agricultural activities, or mining activities, the production of polluting compounds is high, and above all in the steps of transforming, transporting or storing raw materials, both organic compounds (lubricating oil, fuels, chlorinated solvents, monocyclic and polycyclic aromatic compounds, dioxins, polychlorobiphenils, etc.), and inorganic compounds (heavy metals, ionic compounds) are spread in the environment. In particular, agricultural and breeding practices can compromise the environment quality following the use of pesticides, fungicides, nitrates, phosphates, fertilizers, etc.
It is also known that the subsoil quality, and in particular the aquifers quality, is compromised by storage of wastes, fuels and chemical products, by the migration of substances spread in the atmosphere and falling on the ground, and by the release of substances, even harmless, suitable to trigger some chemical or physical processes, or microorganism-mediated processes, which generate an increase of mobility of toxic substances or of substances with an anthropic origin, or of carcinogenic substances naturally present in the aquifers, such as for example contaminations from arsenic or other heavy metals.
The reclamation of subsoil in general, and of aquifers in particular, is often difficult due to the high depth of contamination and the high volumes to be treated, which often make excavation and disposal operations in a tip, scarcely economical and technically unfeasible.
Injection techniques are known, which are aimed to reclamation and decontamination of polluted sites, characterized by driving into the subsoil substances, which are able to degrade the contaminants and/or to accelerate their removal or reduce their toxicity, by generating reactive zones.
A first known mode for performing the injecting techniques is providing to inject reagents inside traditional piezometers (or wells) equipped with single or double packers, suitable to prevent the reagents/amendants from going out of the pipe itself. The piezometers are equipped with screen adapted to make the reacting material go out and a blind section above, cemented to prevent the reflow of reacting material along preferential pathways with higher hydraulic conductivity. The disadvantages of the injecting technique mainly consist in the non-homogeneous distribution of the reacting product in the subsoil, and in the impossibility of selectively injecting the reacting product at the selected depths.
A second known mode for performing the injecting techniques is providing for the use of direct push systems, which allow injecting the reacting products directly inside rods during the perforation step, like the one, for example, disclosed in U.S. Pat. No. 5,133,625.
Moreover, the perforation rods, coupled with suitable pumps, allow reaching high injecting pressure values, and allow an injection mode of the reacting products from bottom to top, in which the perforation rods are firstly planted down the maximum injecting depth and then lifted simultaneously with the action of the pump for injecting the reacting product; the product injection goes on at the same depth till one reaches the reacting product volume required in the technical project specifications, and possibly the perforation rods are again lifted till the following injection range. With the mode, the reagent is not homogeneously distributed and tends to get accumulated in the aquifer layers provided with higher permeability. Finally, the perforation rods also allow an injection mode of the reagent from top to bottom, in which the perforation rods are planted at the minimum injecting depth and the reacting product is injected into the ground till the desired volumes are reached, the rods being then further planted in the ground and the procedures of injecting the reagents are repeated, this step being repeated till the selected depth is reached. With the injection mode, the reagent is uniformly distributed along the vertical injection line, but more slowly in the layers with lower permeability.
The injection by direct push system has a maximum limit of perforation depth as function of the types of grounds being found: consequently, the use of the planting rods does not guarantee to reach the desired depth necessary for injecting the reacting product.
It is known that the reacting products perform their properties in wide time ranges: therefore, following injections in time are necessary, which imply the need of repeating the perforation operation, with a strong increase of costs.
A third injection mode is also known, such as dosing on the water table of the aquifer, initially performed through a suitable excavation to emerge the aquifer by about 50 cm, and afterwards by dividing the excavation into sectors by making ground curbs, for the correct dosing of the reacting mixture. Wetting of the product with grid follow, by directing the jet of mixture parallel and then perpendicular to the excavation edges till the mixture is finished. The same modes are then performed on the following sector part; when the dosing activities for the reacting product are ended, closing is performed for the sectors through a re-closure of the excavation with an excavator.
It is clear how the use of the injection modes is limited only to localized and surface contaminations, not being able to reach the different depth of aquifer or of subsoil.
A last injection mode is also known, which consists in emplacing permeable reactive barriers, by making an excavation of trenches, afterwards filled with reactive material at solid state, such as for example zero-valent iron, like the one disclosed in U.S. Pat. No. 5,266,213. The reactive material is crossed by contaminated water which moves due the effect of the natural hydraulic gradient.
The reagents emplacing technics do not easily allow reaching high depths, and has are characterized by design and construction costs which are higher than those related to the other, above described methodologies.
Injection procedures and systems are also known in the art, which are related to the geotechnical consolidation, such as for example:
WO2008123674, in which a system is disclosed for injecting a concrete mixture equipped with an injection piping, which allows injecting into the subsoil only products adapted to consolidate the subsoil;
EP0623708, which discloses a system for injecting a concrete mixture equipped with a valve pipe and with an electronic device arranged along the tube, suitable to monitor the behaviour of the injections. The system has only the features as to reduce at a minimum the interferences with the electronic device, such as for example the injecting tube made of materials permeable to electromagnetic waves;
FR2444873, which discloses a device equipped with a ball which, under the injection thrust of the injected solidifying liquid, flows downwards, opening the injection hole of the first tube section, thereby allowing the concrete mixture to go out. With the increase of pressures, the deformable ball falls in the below tube sections, having smaller and smaller diameters, and opening, when the pressure increases, the deeper injection holes. The device allows selectively injecting at the desired depths, but do not allow checking the amounts of injected product, since, when the ball slides downwards, due to the pressure increase, the above hole remains open and injection in the above layers is repeated many times;
U.S. Pat. No. 4,442,895, which discloses a method for fracturing the ground and a pressurizing system suitable for reaching the pressure values as to enable fracturing. Fracturing of the surrounding ground is performed through the method, but does not prevent a diffusion along preferred ways for a possible injected concrete mixture;
FR2552462, which discloses a system for injecting concrete, resins, liquids, through the use of a threaded pipe equipped with holes for injecting materials for consolidating the ground. The system is equipped with valves integrated in the injection piping by melting when making the pipe, or by a following mechanical working;
U.S. Pat. No. 5,624,209, which discloses a methodology for injecting fluids in the ground through two coaxial piping, inserted into the ground down to a desired depth, each piping being equipped with holes in the terminal part of the piping. The methodology cannot be used in relation to aquifers, enabling the rising of aquifer water inside the piping; moreover, the methodology cannot be used for the selective injection at the desired depths since the coaxial piping are equipped with a single injection hole.
It is clear that the above systems and procedures related exclusively to consolidate the grounds are characterized by components composed of materials preferably suitable for the purpose of consolidating the grounds, and which does not allow a selective injection at the desired depths and do not ensure an optimum injection free from reflows and dispersions of the injected product, mandatory feature in the injection processes of reacting products for reclaiming contaminated sites.
JP-A-2010 063978 discloses an injection process free from hollow spaces and operating due to the mutual cooperation of an external injection pipe with entries and an injection pipe inside it.
Therefore, object of the present invention is solving the above prior art problems, by providing a process for treating contaminated subsoil, and contaminated aquifers and/or capillary fringes.
A further object of the present invention is providing a treatment process capable of selectively injecting an amount of reacting products at the required project depths.